2How does trees on the fertile plain obtain their nutrients ? Or the cacti in the desserts ?Or the algae in the sea ?
3Review Question Which mode of nutrition do the green plants carry out? A. Autotrophic nutritionB. Heterotrophic nutrition
4Sorry! You’re wrong!Heterotrophic nutrition is the mode of nutrition in which organisms have to depend on other organisms or dead organic matters as their food sources. Green plants, however, can make organic food by themselves using simple inorganic substances.
5Very Good! Photosynthesis Autotrophic nutrition is the mode of nutrition in which organisms can make organic food by themselves using simple inorganic substances.The process by which the green plants obtain nutrients is called :Photosynthesis
6Nature of photosynthesis Takes place in ChloroplastNecessary factors :Carbon dioxideWaterSunlightChlorophyll
10Light reaction Light energy is trapped by chlorophyll in chloroplast Light energy absorbed by chlorophyll splits water molecules into hydrogen and oxygenOxygen is released as a gas through stoma to outsideHydrogen is fed into dark reaction
16carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose)release energy by respiration
17carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose)convert into starch for storage because glucose is not a very good storage molecule
18carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose)change into sucrose and is transported to other parts through phloem
19carbon dioxide and water photosynthesiscarbohydrates (e.g. glucose)fatty acidsglycerolcombine to form fats and oils to form cell membranes and as a food store
20join together to become protein molecules carbon dioxide and waterphotosynthesismineral salts from soil(e.g. NO3-, SO42-)carbohydrates (e.g. glucose)amino acidsjoin together to become protein molecules
22DestarchingReason:To avoid any existing starch in the leaves interfering with the result, and to show that any starch found after the experiment is produced during the period of investigationMethod:By placing the plant in dark for at least 48 hours
23To test a leaf for the presence of Starch Investigation 8.1To test a leaf for the presence of Starch
24Why is the leaf first boiled in water ? boiling waterturn off Bunsen burnerboiling alcoholhot wateriodinewhite tileWhy is the leaf first boiled in water ?Ans: Because the process can soften the leaf, break down the cuticle and kill the leaf.
25Why is the leaf then boiled in alcohol ? boiling waterturn off Bunsen burnerboiling alcoholhot wateriodinewhite tileWhy is the leaf then boiled in alcohol ?Ans: To decolourize the leaf (to remove chlorophyll).
26Ans: Because alcohol catches fire easily. boiling waterturn off Bunsen burnerboiling alcoholhot wateriodinewhite tileWhy is it important to turn off the Bunsen burner when you are heating the alcohol ?Ans: Because alcohol catches fire easily.
27Why is the leaf put in hot water after being boiled in alcohol ? boiling waterturn off Bunsen burnerboiling alcoholhot wateriodinewhite tileWhy is the leaf put in hot water after being boiled in alcohol ?Ans: Since the leaf becomes brittle after boiling in alcohol, so dipping it into hot water enables it to be softened.
28What colour change can be observed if starch is present ? boiling waterturn off Bunsen burnerboiling alcoholhot wateriodinewhite tileWhat colour change can be observed if starch is present ?Ans: The leaf becomes blue-black when iodine solution is added to it.
29To show that Chlorophyll is necessary for Photosynthesis Investigation 8.3To show that Chlorophyll is necessary for Photosynthesis
30Ans: Only the green part. purple partWhich part of the leaf turns blue-black when treated with iodine solution ?Ans: Only the green part.
31Is chlorophyll necessary for photosynthesis ? green partpurple partIs chlorophyll necessary for photosynthesis ?Ans: Yes.
32What is the control in this experiment ? green partpurple partWhat is the control in this experiment ?Ans: The green part of the leaf acts as the control.
33To show that Carbon Dioxide is necessary for Photosynthesis Investigation 8.4To show that Carbon Dioxide is necessary for Photosynthesis
34Why is potassium hydroxide solution put in one of the flasks ? sunlightBAwaterpotassium hydroxide solutionWhy is potassium hydroxide solution put in one of the flasks ?Ans: To absorb all the carbon dioxide in flask B.
35sunlightBAwaterpotassium hydroxide solutionWhat happens to each leaf after testing the presence of starch at the end of the experiment ?Ans: The leaf in flask A changes to blue-black while the leaf in flask B stains brown.
36Ans: Carbon dioxide is necessary for photosynthesis. sunlightBAwaterpotassium hydroxide solutionWhat do your results suggest about the relationship between carbon dioxide and photosynthesis ?Ans: Carbon dioxide is necessary for photosynthesis.
52palisade mesophyll (layer) columnar cells closely packed togetherabsorb light more efficientlycontains many chloroplasts
53spongy mesophyll (layer) irregular cells loosely packed together to leave numerous large air spacesallow rapid diffusion of gases throughout the leafsome (fewer than palisade mesophyll) chloroplasts for photosynthesisspongy mesophyll (layer)
54same as upper epidermis except the cuticle is thinner lower epidermis
55opening which allows gases to pass through it to go into or out of the leaf stoma (stomata)
63The leaf is broad & flattened The leaf is thindecrease diffusion distance for gases & lightThe leaf is broad & flattenedincrease surface area to absorb more sunlight
64Cuticle exists in upper epidermis and is transparent Allows most light to pass into photosynthetic mesophyll tissues
65Palisade mesophyll cells are closely packed and contain many chloroplasts To carry out photosynthesis more efficiently
66Spongy mesophyll cells are loosely packed with numerous large air spaces To allow rapid diffusion of gases throughout the leaf
67Numerous stomata on lower epidermis To allow rapid gaseous exchange with the atmosphere
68Extensive vein systemAllow sufficient water to reach the cells in the leafTo carry food away to other parts of the plant
69Mineral requirements in plants In order to synthesize amino acids, nitrate ions which must be taken into the plant from the soil through the rootOther minerals are also necessary to maintain the life of the plant (N, Mg, P, K, S, etc)
70The importance of nitrogen For synthesis of proteins, chlorophyll, etcTaken in form of nitrate ionsDeficiency symptoms:Little growth ( - no protein made)Yellowing of leaves ( - no chlorophyll made)
71The importance of magnesium Essential component of chlorophyllDeficiency symptoms:Yellowing of leaves (no chlorophyll made)Poor growth (no food manufactured because of lack of chlorophyll)
72Use of fertilizers in agriculture Continuous harvesting crops removes valuable mineral salts from soilFertilizers are added to replace such lossTwo kinds of fertilizers:Natural fertilizersChemical fertilizers
73Natural fertilizers From manure Organic compounds in it are decomposed by the bacteria in soil to form mineral salts
74Chemical fertilizersMainly nitrogenous and phosphorous compounds manufactured artificially
75Comparison between natural and chemical fertilizers Natural fertilizersChemical fertilizersContain humus which can improve soil textureNo humus so cannot improve soil textureLess soluble in water so less likely to be washed awayVery soluble in water so more likely to be washed away
76Comparison between natural and chemical fertilizers Natural fertilizersChemical fertilizersMuch cheaperVery expensiveLess soluble in water so more difficult to be absorbedVery soluble in water so easier to be absorbedTime is needed for the decomposition to complete before nutrients are available to plantsMore readily to be used by the plants